Power headroom report method and apparatus of ue

ABSTRACT

An improved method and an apparatus for reporting Power Headroom (PH) of a UE are provided. The Power Headroom Report (PHR) method of the present invention includes determining whether to trigger PHR based on a change of Power Management Maximum Power Reduction (P-MPR) between two time points, generating, if PHR is determined to be triggered, Power Headroom, and reporting the Power Headroom information to a base station.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of a prior applicationSer. No. 13/396,947, filed on Feb. 15, 2012, which claimed the benefitunder 35 U.S.C. §119(e) of a U.S. Provisional application filed on Feb.15, 2011 in the U.S. Patent and Trademark Office and assigned Ser. No.61/442,985, and of a U.S. Provisional application filed on Feb. 21, 2011in the U.S. Patent and Trademark Office and assigned Ser. No.61/444,844, and of a U.S. Provisional application filed on Apr. 5, 2011in the U.S. Patent and Trademark Office and assigned Ser. No.61/471,872, and of a U.S. Provisional application filed on May 3, 2011in the U.S. Patent and Trademark Office and assigned Ser. No.61/481,878, the entire disclosure of each of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a Power Headroom Report (PHR) methodand apparatus of a User Equipment (UE). More particularly, the presentinvention relates to a method and apparatus for reporting Power Headroom(PH) of a UE efficiently.

2. Description of the Related Art

Mobile communication systems are developed to provide subscribers withvoice communication services on the move. With the advance oftechnologies, the mobile communications have evolved so as to supporthigh speed data communication services as well as the standard voicecommunication services.

Recently, as one of the next generation mobile communication systems,Long Term Evolution (LTE) is on the standardization by the 3rdGeneration Partnership Project (3GPP). LTE is designed to provide for adownlink speed of up to 100 Mbps. In order to fulfill the requirementsof the LTE systems, studies have been done in various aspects, includingminimization of the number of involved nodes in the connections, andplacing the radio protocol as close as possible to the radio channels.

In the meantime, unlike the standard voice service, most data servicesare allocated resources according to the amount of data to betransmitted and to the channel condition. Accordingly, in the wirelesscommunication system such as cellular communication system, it isimportant to manage resource allocation based on the resource scheduledfor data transmission, the channel condition, and the amount of data tobe transmitted. This is the fact even in the LTE system, and even if thebase station scheduler manages and assigns radio resources.

More recent studies are focused on the LTE-Advanced (LTE-A) forimproving data rate with the adaptation of several new techniques.Carrier Aggregation (CA) is one of the most distinct features of LTE-A.Unlike communication systems according to related art that use singleuplink and single downlink carriers per a User Equipment (UE), theCarrier Aggregation enables a UE to be scheduled on multiple carriers inboth uplink and downlink. Accordingly, it is required for the eNB toconfigure the UE transmit power per uplink carrier efficiently and, as aconsequence, it becomes more important for the UE to report maximum UEtransmit power and Power Headroom (PH).

Meanwhile, LTE UEs are generally configured to be equipped with multiplesystem modems enabling operation in dual mode. This configuration allowsthe UE to simultaneously receive multiple services through two differentsystems. In such a situation, the UE is required to report the maximumtransmit power and Power Headroom (PH) per system in order to improvescheduling reliability.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present invention.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide a method and apparatus for reporting PowerHeadroom (PH) of the UE efficiently.

In accordance with an aspect of the present invention, a Power HeadroomReport (PHR) method of a terminal is provided. The method includesdetermining whether to trigger a PHR based on a change of PowerManagement Maximum Power Reduction (P-MPR) between two time points,generating, if PHR is determined to be triggered, a Power Headroom (PH),and reporting the Power Headroom information to a base station.

In accordance with another aspect of the present invention, a PowerHeadroom Report (PHR) apparatus of a terminal is provided. The apparatusincludes a transceiver for communicating with a base station, and acontroller for determining whether to trigger a PHR based on a change ofPower Management Maximum Power Reduction (P-MPR) between two timepoints, for generating, if PHR is determined to be triggered, a PowerHeadroom (PH), and for reporting the Power Headroom information to abase station.

In accordance with another aspect of the present invention, anon-transitory computer readable storage medium of a terminal storing aprogram for reporting a Power Headroom (PH) to a base station isprovided. The program stored on the non-transitory computer readablestorage medium comprises instructions to cause a computer to determinewhether to trigger a PHR based on a change of Power Management PowerReduction (P-MPR) between two time points, generate, if the PHR isdetermined to be triggered, the Power Headroom, and report the PowerHeadroom to the base station.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram illustrating an architecture of a mobilecommunication system according to an exemplary embodiment of the presentinvention.

FIG. 2 is a diagram illustrating a protocol stack of a mobilecommunication system according to an exemplary embodiment of the presentinvention.

FIG. 3 is a diagram illustrating an exemplary situation of CarrierAggregation in a mobile communication system according to an exemplaryembodiment of the present invention.

FIG. 4 is a diagram illustrating transmit power configuration caused byunfair scheduling in a method according to the related art.

FIG. 5 is a signaling diagram illustrating a Power Headroom Report (PHR)procedure according to an exemplary embodiment of the present invention.

FIG. 6 is a diagram is a diagram illustrating a Power Headroom Report(PHR) triggered by variation of a Power Management Maximum PowerReduction (P-MPR) in a Power Headroom Report method according to anexemplary embodiment of the present invention.

FIG. 7 is a diagram illustrating a structure of an extended PowerHeadroom Report (PHR) Medium Access Control (MAC) Control Element (CE)for use in a Power Headroom Report (PHR) method according to anexemplary embodiment of the present invention.

FIG. 8 is a flowchart illustrating a Power Headroom Report (PHR) methodaccording to an exemplary embodiment of the present invention.

FIG. 9 is a flowchart illustrating a Power Headroom Report (PHR) methodaccording to an exemplary embodiment of the present invention.

FIG. 10 is a flowchart illustrating a Power Headroom Report (PHR) methodaccording to an exemplary embodiment of the present invention.

FIG. 11 is a block diagram illustrating a configuration of an UserEquipment (UE) according to an exemplary embodiment of the presentinvention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Before explaining exemplary embodiments of the present invention, adescription is made of to Long Term Evolution (LTE) mobile communicationsystem with reference to FIGS. 1, 2, and 3.

FIG. 1 is a diagram illustrating an architecture of a mobilecommunication system according to an exemplary embodiment of the presentinvention.

Referring to FIG. 1, the radio access network of the mobilecommunication system includes evolved Node Bs (eNBs) 105, 110, 115, and120, a Mobility Management Entity (MME) 125, and a Serving-Gateway(S-GW) 130. The User Equipment (UE) 135 connects to an external networkvia eNBs 105, 110, 115, and 120, and the S-GW 130.

The eNBs 105, 110, 115, and 120 correspond to legacy node Bs of aUniversal Mobile Communications System (UMTS). The eNBs 105, 110, 115,and 120 allow the UE to establish a radio link and are responsible forcomplicated functions as compared to the legacy node B. In the LTEsystem, all the user traffic including real time services such as Voiceover Internet Protocol (VoIP) are provided through a shared channel.Thus, there is a need for a device which is located in the eNB toschedule data based on the state information such as UE bufferconditions, Power Headroom state, and channel state. Typically, one eNBcontrols a plurality of cells. In order to secure a data rate of up to100 Mbps, the LTE system adopts Orthogonal Frequency DivisionMultiplexing (OFDM) as a radio access technology. Also, the LTE systemadopts Adaptive Modulation and Coding (AMC) to determine the modulationscheme and channel coding rate in adaptation to the channel condition ofthe UE.

S-GW 130 is an entity to provide data bearers so as to establish andrelease data bearers under the control of the MME 125. MME 125 isresponsible for various control functions and is connected to aplurality of eNBs 105, 110, 115, and 120.

FIG. 2 is a diagram illustrating a protocol stack of a mobilecommunication system according to an exemplary embodiment of the presentinvention.

Referring to FIG. 2, the protocol stack of the LTE system includesPacket Data Convergence Protocol (PDCP) 205 and 240, Radio Link Control(RLC) 210 and 235, Medium Access Control (MAC) 215 and 230, and Physical(PHY) 220 and 225. The PDCP 205 and 240 is responsible for IP headercompression/decompression. The RLC 210 and 235 is responsible forsegmenting the PDCP Protocol Data Unit (PDU) into segments ofappropriate size for an Automatic Repeat Request (ARQ) operation. TheMAC 215 and 230 is responsible for establishing connection to aplurality of RLC entities so as to multiplex the RLC PDUs into MAC PDUsand demultiplex the MAC PDUs into RLC PDUs. The PHY 220 and 225 performschannel coding on the MAC PDU and modulates the MAC PDU into OFDMsymbols to transmit over radio channel or performs demodulating andchannel-decoding on the received OFDM symbols and delivers the decodeddata to the higher layer.

FIG. 3 is a diagram illustrating an exemplary situation of CarrierAggregation in a mobile communication system according to an exemplaryembodiment of the present invention.

Referring to FIG. 3, typically an eNB can use multiple carrierstransmitted and received in different frequency bands. For example, theeNB 305 can be configured to use the carrier 315 with center frequencyfl and the carrier 310 with center frequency f3. If Carrier Aggregationis not supported, the UE 330 has to transmit/receive data using one ofthe carriers 310 and 315. However, the UE 330 having the CarrierAggregation capability can transmit/receive data using both the carriers310 and 315. The eNB can increase the amount of the resource to beallocated to the UE having the Carrier Aggregation capability inadaptation to the channel condition of the UE so as to improve the datarate of the UE.

If a cell is configured with one downlink carrier and one uplink carrieraccording to the related art, the Carrier Aggregation can be understoodas though the UE communicates data via multiple cells. With the use ofCarrier Aggregation, the maximum data rate increases in proportion tothe number of aggregated carriers.

In the following description, the phrase “the UE receives data through acertain downlink carrier or transmits data through a certain uplinkcarrier” refers to transmission or receipt of data through control anddata channels provided in a cell corresponding to center frequencies andfrequency bands of the downlink and uplink carriers. In the followingdescription, the Carrier Aggregation is expressed as a procedure ofconfiguring a plurality of serving cells with the terms such as primaryserving cell, secondary serving cell, and activated service cell. Theseterms are used with the meanings as specified in TS 36.331 and TS 36.321released on December 2011, the entire disclosure of which isincorporated herein.

In LTE, the UE's available transmit power amount is referred to as PowerHeadroom (PH) which is defined as the difference between a configuredmaximum UE output power (PCMAX) and a transmit power currently beingused by the UE. If a specific condition is satisfied, the UE reports PHto the eNB. The process of the UE reporting PH to the eNB is referred asa Power Headroom Report (PHR). In a method according to the related art,the PHR is triggered when pathloss variation is greater than apredetermined threshold value or when a PHR period arrives. The eNB canpredict the channel state of the eNB based on the collected PH values todetermine whether to allocate an additional radio resource.

Because PH varies according to various reasons such as configuredmaximum UE output power variation, pathloss variation, and TPC error,the eNB's PH variation detection failure causes unfair resourceallocation.

FIG. 4 is a diagram illustrating transmit power configuration caused byunfair scheduling in a method according to the related art.

Reference number 400 denotes the UE's power usage. The configuredmaximum UE output power P_(CMAX) 410 is a value set between the upperbound P_(CMAX) _(—) _(H) 405 and a lower bound P_(CMAX) _(—) _(L) 415based on the parameters provided by the eNB and predeterminedparameters. The UE transmits data with the Modulation and Coding Scheme(MCS)=m on the allocated radio resource of x resource blocks (RBs) attime t1. At this time, the used power 420 is very low as compared to theconfigured maximum UE output power. If a specific condition issatisfied, then the UE reports to the eNB the PH 445, (i.e., thedifference between the configured maximum UE output power and the usedpower 420). The eNB determines that the configured maximum UE outputpower is not short even though much of the radio resource is allocatedto the UE, based on the PH. In order to provide the service at higherdata rate, the eNB further allocates y RBs to the UE with a higher MCSlevel of n. However, the configured maximum UE output power P_(CMAX) 440decreases while the used power 435 increases such that P_(CMAX) 440becomes less than the used power 435 at time t2. As an example, the usedpower 435 at time t2 is also greater than the lower bound P_(CMAX) _(—)_(L) 450. At time t2, the configured maximum UE output power P_(CMAX)440 is a value set between the upper bound P_(CMAX) _(—) _(H) 430 and alower bound P_(CMAX) _(—) _(L) 450 based on the parameters provided bythe eNB and predetermined parameters.

The P_(CMAX) 440 becomes less than the used power 435 at time t2 becausethe configured maximum UE output power 440 has changed according to thevariations of number and locations of scheduled Physical Resource Blocks(PRBs), system bandwidth, frequency band, and number of scheduledcarriers. This problem can be solved in such a manner that the UEreports the PH and configured maximum UE output power to the eNB at anappropriate time point such that the eNB performs uplink scheduling onthe UE in consideration of the time-varying configured maximum UE outputpower. One of the factors influencing the P_(CMAX) is Power ManagementMaximum Power Reduction (P-MPR). Exemplary embodiments of the presentinvention provide a method and apparatus for reporting to the eNBwhether the P-MPR is changed at an appropriate time point.

In order to determine the factors influencing the configured maximum UEoutput power, it is necessary to check the criteria for determining theconfigured maximum UE output power. For example, once the P_(CMAX) _(—)_(H) and P_(CMAX) _(—) _(L) are determined according to the parametersprovided by the eNB and predetermined parameters, the UE may determineP_(CMAX) within the bounds provided in Equations 1, 2, and 3.

P _(CMAX) _(—) _(L) ≦P _(CMAX) ≦P _(CMAX) _(—) _(H)  (1)

where P_(CMAX) _(—) _(H) and P_(CMAX) _(—) _(L) are defined as follows:

P _(CMAX) _(—) _(L)=MIN{P _(EMAX) −T _(C) ,P_(PowerClass)−MAX(MPR+A-MPR,P-MPR)−T _(C)}  (2)

P _(CMAX) _(—) _(H)=MIN{P _(EMAX) ,P _(PowerClass)}  (3).

P_(EMAX) is maximum allowed UE output power in, for example,SystemInformationBlockType1 (SIB1) broadcasted by the eNB.P_(PowerClass) is maximum UE power specified without taking into accountthe tolerance. P_(CMAX) _(—) _(H) is defined as the minimum valuebetween P_(EMAX) and P_(PowerClass).

Meanwhile, P_(CMAX) _(—) _(L) is somewhat complex. P_(CMAX) _(—) _(L) isinfluenced by MPR+A-MPR and P-MPR. Δ T_(C), MPR, and A-MPR are theparameters for defining the ceiling value to adjust maximum UEtransmission power on the serving cell such that the unintendedradiation or interference to adjacent channel meet to a predeterminedrequirement. MPR is the value determined according to the amount oftransmission resource allocated to the UE and modulation scheme. A-MPRis the value determined according to uplink frequency band, geographicalcharacteristic, and uplink transmission bandwidth. A-MPR is used for thecase of frequency band particularly sensitive to ambient spuriousradiation. Δ T_(C) is the parameter for allowing additional transmissionpower adjustment in case where uplink transmission is performed at anedge of the frequency band. For example, if uplink transmission isperforms on the lowest 4 MHz or the highest 4 MHz of a certain frequencyband, the UE sets Δ T_(C) to 1.5 dB and, otherwise, UE sets Δ T_(C) to0.

P-MPR is a maximum power reduction value applied for satisfying SpecificAbsorption Rate (SAR) requirement and is determined in consideration ofthe distance between the device and human body. For example, if thedistance between the device and human body is short, then the totaltransmission power value of the UE should decrease and, for this, a highvalue of P-MPR is applied. In contrast, if the distance between thedevice and the human body is long, then it is tolerable to increase thetotal transmit power value of the device such that P-MPR is set to a lowvalue. P-MPR is associated with the power control such that whenmultiple carriers are used or data transmission is performed along withother system modem the maximum power allocated per carrier or system isrestricted. Such influence is reflected to P-MPR.

Accordingly, the configured maximum UE output power PCMAX is mainlyinfluenced by two factors. For example, the configured maximum UE outputpower PCMAX may be mainly influenced by the MPR+A-MPR related to theout-of-band emission requirement, and by the P-MPR related to the powermanagement. Because the eNB cannot predict the variation of P-MPR, theUE reports, when detecting variation of P-MPR over a predeterminedthreshold, the PH variation amount (or PH) to the eNB. Also, becauseonly the PH is not enough for determining the power actually used by theUE, the UE reports the configured maximum UE output power too. Also, byindicating which of p-MPR and MPR+A-MPR is mainly used for determiningthe maximum transmit power, the eNB can observe the variation of theconfigured maximum UE output power and record the result in a databaseto remove the influence of the P-MPR.

FIG. 5 is a signaling diagram illustrating a Power Headroom Report (PHR)procedure according to an exemplary embodiment of the present invention.

In the mobile communication system including an UE 505 and an eNB 510,the eNB 510 firsts configures the UE in consideration of the UEcapability and network status at step 515. At this time the eNB 510 canconfigure Carrier Aggregation (CA) and PHR of the UE 505. If multipleuplink carriers are configured for the eNB 505 (i.e., if multipleserving cells having uplink resources are configured), then the eNB 510can configure the UE to use an extended PHR function or an extended PHRMAC CE. In order to configure the extended PHR, the eNB 510 provides theinformation related to PHR as follows:

(a) phr-Config

-   -   periodicPHR-Timer: A timer value for periodic PHR report. The        expiry of this timer triggers PHR.    -   prohibitPHR-Timer: A timer value for avoiding PHR reports that        are too frequent (i.e., a timer so as to limit the frequency of        PHR reports). No new PHR is triggered while this timer is        running    -   dl-PathlossChange: A new PHR is triggered when the variation of        uplink pathloss is equal to or greater than this value. Or, a        new PHR is triggered when the variation of P-MPR is equal to or        greater than this value.

(b) extendedPHR: This indicates whether an extended PHR is used.

Upon receipt of the control message, the UE 505 configures downlink anduplink and continues normal operations according to the instruction fromthe eNB 510.

Afterward, the UE 505 is allocated transmission resource for new uplinktransmission at step 520 and determines whether PHR condition issatisfied at step 525. The PHR condition is fulfilled in the followingcases:

(a) expiry of periodicPHR-Timer

(b) the prohibitPHR-Timer is not running and the amount of downlinkpathloss of the serving cell providing pathloss among the serving cellsactivated and configured with uplinks is equal to or greater thandl-PathlossChange as compared to the previous PHR.

(c) the prohibitPHR-Timer is not running and there is a serving cellfulfilling the following conditions among the serving cells activatedand configured with uplinks:

-   -   uplink transmission is performed in the last PHR report and        current PHR report    -   a difference between the transmit power reduction related to        P-MPR in the uplink transmission with the last PHR (or allowed        by P-MPR) and the transmit power reduction related to P-MPR in        the current uplink transmission is equal to or greater than        dl-PathlossChange.

A description is made of the third condition (c) in more detailhereinafter with reference to FIG. 6.

FIG. 6 is a diagram is a diagram illustrating a Power Headroom Report(PHR) triggered by variation of a Power Management Maximum PowerReduction (P-MPR) in the Power Headroom Report method according to anexemplary embodiment of the present invention.

In order to determine uplink transmit power for a certain serving cellwhile observing various restrictions, the UE performs power reduction orpower backoff, and the power reduction amount is determined according tothe parameters such as MPR, A-MPR, and P-MPR. The parameters related tothe power reduction in a certain service cell change according towhether uplink transmission takes place actually on the serving cell.

For example, when no actual uplink transmission takes place, powerbackoff is not applied as denoted by reference number 620. Accordingly,the various transmit power parameters including P-MPR are set to 0. Incontrast, when actual uplink transmission takes place, the power backoffvalue is determined in consideration of P-MPR satisfying the SARrequirement. In PHR, the UE reports PH and P_(CMAX) in all of theactivated serving cells with configured uplinks at the correspondingtime point. Accordingly, even though no actual uplink transmission takesplace in a serving cell at the time when generating PHR, P-MPR isdetermined. Of course, the P-MPR is not an actual P-MPR but apredetermined value (i.e., 0).

By taking an example of PHR at certain time points A 605 and B 610,suppose a situation in which an actual transmission takes place at atime point A as denoted by reference number 625 and no actualtransmission at a time point B in a certain serving cell. In this case,the real P-MPR is applied at the time point A while the P-MPR set to 0is applied at the time point B such that, although the transmit powerreduction related to the real P-MPR is tiny (i.e., although thetransmission power reduction value related to P-MPR is not changednearly if actual uplink transmission takes place at the time point B inthe corresponding serving cell), the UE can determine that arithmeticvariations of P-MPR is equal to or greater than a predeterminedthreshold. As a consequence, PHR is transmitted unnecessarily.

Such a problem occurs in all the cases in which P-MPR is set to 0 due tono actual transmission takes place at least one of time points A and B(such as those instances denoted by reference numbers 625, 635, and640). In exemplary embodiments of the present invention, PHR istriggered in consideration of the variation amount of the transmit powerreduction related to P-MPR. However, PHR is triggered in considerationof the variation amount of the transmit power reduction related to P-MPRonly when the actual transmission takes place at both the two timepoints (i.e., A and B as denoted by reference number 630).

If the PHR condition is fulfilled, the UE 505 generates a PHR MAC CE atstep 530. Because the UE is instructed to use extended PHR MAC CE in PHRconfiguration process, the UE calculates PH per serving cell usingEquation 4 in consideration of the P_(CMAX,c) and required transmitpower of the activated serving cells and configured to have uplink.

PH(i)=P _(CMAX,c)(i)−{10 log₁₀(M _(PUSCH,c)(i))+P _(O) _(—)_(PUSCH,c)(j)+α_(c)(j)·PL _(c)+Δ_(TF,c)(i)+ƒ_(c)(i)}  (4)

PH(i) of i^(th) subframe in serving cell c is calculated based on thepower offset Δ_(TF,c) derived from MCS, pathloss PL_(c), and accumulatedTransmit Power Controls (TPCs) f_(c)(i). In Equation 4, PL_(c) denotesthe path loss of the cell configured to provide the pathloss for theserving cell c. The pathloss used for determining uplink transmit powerof a certain serving cell is the pathloss of the uplink channel of thecorresponding cell or the path loss of the downlink channel of anothercell. The eNB selects the pathloss to be used and notifies the UE of theselected pathloss in the call setup process.

In Equation 4, f_(c)(i) is the accumulated value of the Transmit PowerControl (TPC) on the serving cell c. PO_PUSCH,C denotes a parameter ofhigher layer as sum of cell-specific and UE-specific values. Typically,PO_PUSCH,C has a value determined according to the type of PhysicalUplink Shared Channel (PUSCH) such as semi-persistent scheduling,dynamic scheduling, and random access response. α_(c) is a 3-bitcell-specific value representing a weight applied to the pathloss forcalculating uplink transmit power (i.e., the higher this value is themore the pathloss influence increases) and its value is restrictedaccording to the type of the PUSCH transmission. For example, this valueis set to j=0 for semi-persistent scheduling, j=1 for dynamicscheduling, and j=2 for random access response.

For the serving cell having no actual transmission, PH is calculatedwith P_(CMAX,c) determined with zero transmit power reduction and therequired transmit power using predetermined values of M_(PUSCH,c)(i) andΔ_(TF,c) (e.g., a value indicating the lowest MCS level and 1 transportblock).

The UE inserts the PH and other information per serving cell in theextended PHR MAC CE.

FIG. 7 is a diagram illustrating a structure of an extended PowerHeadroom Report (PHR) Medium Access Control (MAC) Control Element (CE)for use in a Power Headroom Report (PHR) method according to anexemplary embodiment of the present invention.

In case of reporting PHs for multiple serving cells in a mobilecommunication system supporting Carrier Aggregation, it is advantageousto transmit the multiple PHs in a single PHR in view of trafficoverhead. Unlike the normal MAC CE, the extended PHR MAC CE is designedto report PHs and P_(CMAX,c) for multiple cells. In FIG. 7, referencenumbers 700 to 730 (i.e., 700, 705, 710, 715, 720, 725, and 730) denotea bitmap indicating PHs for the serving cells that are included in thecorresponding PHR. Each bit of the bitmap corresponds to SCell indexindicating a SCell. Reference number 750 denotes a P bit indicatingwhether the configured maximum UE output power P_(CMAX) is influenced bythe P-MPR according to an exemplary embodiment of the present invention.

Although there is no actual PUSCH transmission, the eNB can trigger PHRto acquire pathloss on a specific uplink carrier. Such a PHR trigger canbe implemented by defining a transmission format (transmission resourceamount and MCS level) for use in PH calculation. In order to interpretthe reported PHs correctly, the eNB has to know whether the per-cell PHincluded in the PHR is calculated in consideration of real PUSCHtransmission or using a predetermined transmission format. Referencenumber 740 denotes a V bit which is 1-bit indicator for indicatingwhether the PH is calculated in consideration of real PUSCHtransmission. In PHR, the UE sets the V bit to a predetermined value(e.g., 0) if the UE calculates the PH for the corresponding cell basedon the real PUSCH transmission (i.e. using real transmission format) oranother value (e.g. 1) if the UE calculates the PH for the correspondingcell using the reference format (i.e., number of RBs=1 and Δ_(TF)=0)because of no real PUSCH transmission in the corresponding cell.

Reference numbers 745 and 755 are PH and P_(CMAX) respectively. The PHsfor the individual carriers are arranged in unit of byte in ascendingorder of index (i.e., type 2 PH and P_(CMAX) for PCell, type 1 PH 760and P_(CMAX) 765 for PCell, PH 770 and P_(CMAX) 775 for SCell having thelowest index, PH and P_(CMAX) for SCell having the second lowest index,PH and P_(CMAX) for SCell having the third lowest index, and PH andP_(CMAX) for SCell having the fourth lowest index). The type 2 PH isreported only for the PCell and calculated in consideration of PUCCHrequirement transmit power as well as PUSCH requirement transmit power.Reference number 407 denotes an R bit indicating reserved bit.

At step 535, the UE generates a MAC PDU, multiplexes the PHR MAC CE inthe MAC PDU. The UE transmits the MAC PDU to the eNB at step 540. The UErecords the information on the pathloss, P_(CMAX), P-MPR, and whetherthe PH is calculated in consideration of real data transmission that areapplied in PH calculation per serving cell.

At step 545, if the PHR MAC CE is received, the eNB checks theper-serving cell PHs, whether P-MPR is applied or not, and whether PHvariation is caused by P-MPR variation, and allocates uplinktransmission resource in consideration of the check result.

FIG. 8 is a flowchart illustrating a Power Headroom Report (PHR) methodaccording to an exemplary embodiment of the present invention.

The UE receives a control message and configures Carrier Aggregation andextended PHR according to the information carried in the control messageat step 805. The control message includes the control information suchas phr-config and extendedPHR. Afterward, the UE performs normalfollow-up operation.

The UE is allocated uplink transmission resource for new uplinktransmission at step 810 and calculates uplink transmit power at step815. The uplink transmission power is calculated per serving cell. TheUE determines P_(CMAX,c) per serving cell using Equations 1, 2, and 3and determines the required transmit power by referencing a number oftransmission resource blocks, transmission format, and pathloss. Next,the UE selects minimum value between the two values as the transmitpower for the corresponding serving cell.

Afterward, the UE determines whether PHR is triggered at step 820. ThePHR is triggered when the periodicPHR-Timer expires or the change ofuplink pathloss in the service cell in active state and proving pathlossis greater than a dl-PathlossChange as compared to the previous PHRreport. If P-MPR greater than 0 is currently applied or applied in thelast PHR transmission, and if one of the following PHR triggerconditions are fulfilled, then PHR is triggered. If the P-MPR greaterthan 0 is applied, then it is necessary to adjust the LTE transmit powerdue to the uplink transmission by other radio transmission modem.

The PHR trigger conditions include:

-   -   prohibitPHR-Timer expires or has expired, when there is the        activated serving cell satisfying the following conditions:    -   there are UL resources allocated for transmission or there is a        PUSCH transmission on a certain serving cell, and the required        power backoff on this serving cell has changed more than        dl-PathlossChange since the last transmission of a PHR when the        UE has UL resources allocated for transmission or PUCCH        transmission on this cell at the last PHR transmission timing,        the required transmit power backoff for the serving cell is the        required transmit power backoff controlled (or allowed) by        P-MPR.

The required power backoff controlled (or allowed) by P-MPR means thepower backoff to be applied by the UE when only the SAR requirement isconsidered. The required power backoff controlled by P-MPR may differfrom the real power backoff applied. For example, if the power backoffto be applied for fulfilling the neighbor channel interferencerestriction requirement such as MPR and A-MPR at a certain time point isA dB and the power backoff to be applied for fulfilling SAR requirementis B dB, then the required power backoff controlled by P-MPR is B dB.The real power backoff applied by the UE is determined by the maximumvalue between A and B.

Next, the UE calculates PH per serving cell using Equation 4 inconsideration of the P_(CMAX,c) and required transmit power on theactivated serving cells with configured uplink at step 825. The UEgenerates the extended PHR MAC CE with per-serving cell PHs and otherinformation as shown in FIG. 7.

Next, the UE sets P bit to a corresponding value at step 830. The P bitis a 1-bit indicator for indicating whether which of P-MPR and MPR+A-MPRhas contributed to the calculation of P_(CMAX,c) per serving cell. TheP-bit set to 0 if the maximum transmit power is not influenced by P-MPRfor power management, and the P-bit is set to 1 if the maximum transmitpower is influenced by P-MPR. That is, the P bit is set to 1 ifP_(CMAX,c) has a different value due to the influence of P-MPR, and theP-bit is set to 0 if P_(CMAX,c) has the same value regardless of whetherP-MPR is applied or not.

Finally, the UE generates and transmits a MAC PDU at step 835.Afterward, the UE waits for allocation of new uplink transmissionresource. The MAC PDU can include the PHR MAC CE.

According to exemplary embodiments of the present invention, PHR MAC CEcan be categorized into one of two categories: normal PHR MAC CE andextended PHR MAC CE. The normal PHR MAC CE is the PHR MAC CE used beforethe introduction of Carrier Aggregation, and the extended PHR MAC CE isthe PHR MAC CE introduced for transmitting PHs and supplementaryinformation on multiple serving cells. Typically, the normal PHR MAC CEis composed of 2 reserved bits and 6-bit PH field. The extended MAC CEformat is depicted in FIG. 7.

As an example, the network can instruct the UE to use the normal PHR MACCE or extended PHR MAC CE in consideration of the UE capability andcurrent configuration or network state. This can be done by sending theUE the control information of MAC-MainConfig including the informationindicating the use of extended PHR MAC CE (hereinafter, referred to asextendedPHR). This information can indicate one of the four casesdetermined according to the PHR MAC CE format and whether to use CarrierAggregation as follows:

(1) Single serving cell with uplink configuration and normal PHR MAC CE;

(2) Multiple serving cells with uplink configuration and normal PHR MACCE;

(3) Single serving cell with uplink configuration and extended PHR MACCE; and

(4) Multiple serving cells with uplink configuration and extended PHRMAC CE.

The case (2) has no special usefulness but requires determining whichtype of PH should be inserted for which serving cell in the normal PHRMAC CE, resulting in increase of UE implementation complexity. Inexemplary embodiments of the present invention, the case (2) is excludedto reduce UE implementation complexity.

In case in which the UE configured to use the extended PHR MAC CE doesnot support simultaneous transmission of PUCCH and PUSCH, the type 2 PHfield of the PHR MAC CE should be filled with, for example, meaninglessinformation. In order to reduce such overhead, the UE is configured touse the extended PHR MAC CE format having the type 2 PH field when theUE is configured to support simultaneous transmission of PUCCH andPUSCH, and the UE is configured to use the extended PHR MAC CE formathaving no type 2 PH field when the UE is configured not to supportsimultaneous transmission of PUCCH and PUSCH.

As aforementioned, the network instructs the UE to use one of the normaland extended PHR MAC CE according to the UE capability and according tothe current configuration or network state. This means that thecurrently used PHR MAC CE format can be changed. If the normal PHR MACCE format is changed to the extended PHR MAC CE format, it is necessaryto transmit the PHR MAC CE of the new format quickly. According toexemplary embodiments of the present invention, this can be accomplishedby triggering PHR in a new format.

FIG. 9 is a flowchart illustrating a Power Headroom Report methodaccording to an exemplary embodiment of the present invention.

The UE first receives the control information referred as MAC-MainConfigfrom the eNB at step 905. This control information is transmitted to theUE in RRC CONNECTION SETUP message or RRC CONNECTION RECONFIGURATIONmessage. This control information includes configuration informationrelated to the MAC layer functionality such as phr-Config as informationrelated to PHR configuration and extendedPHR.

Next, the UE determines whether the MAC-MainConfig includes extendedPHR(or whether the control message received at step 905 includesextendedPHR information) at step 910 and, if so, the procedure proceedsto step 915 and, otherwise the procedure proceeds to step 935. If thisinformation includes the indicator indicating the use of PHR MAC CEformat, such information means to instruct the UE to use the extendedPHR MAC CE and, otherwise, the UE is instructed to use the normal PHRMAC CE.

At step 915, the UE determines whether the most recently receivedMAC-MainConfig (or a most recently received control message, e.g., RRCCONNECTION SETUP message or RRC CONNECTION RECONFIGURATION message)includes extendedPHR. If it is determined that the extendedPHR isincluded at step 915, then the procedure proceeds to step 930 and,otherwise, the procedure proceeds to step 920. If the most recentlyreceived MAC-MainConfig information includes no extendedPHR, then thismeans that the normal PHR MAC CE is recommended.

If the procedure proceeds to step 920, this means that the PHR MAC CEformat is changed for the normal PHR MAC CE format. The UE triggers PHRand generates PHR MAC CE in extended format when the uplink transmissionresource for new transmission is available at step 920. At this time,the UE determines whether to include type 2 PH according to whethersimultaneous PUSCH and PUCCH transmission is configured. If thesimultaneous PUSCH and PUCCH transmission is configured, the UE includesthe type 2 PH in the extended PHR MAC CE and, otherwise, the UE excludesthe type 2 PH. Next, the UE transmits the extended PHR MAC CE at step925 and terminates the procedure. As an example, the PHR MAC CEgeneration procedure corresponds to step 825 of FIG. 8.

If it is determined that no extendedPHR is included at step 910, thenthe UE determines whether there are multiple serving cells with uplinkcarrier configuration at step 935. If there are multiple serving cellswith uplink carrier configuration, then the procedure proceeds to step940. If there are not multiple serving cells with uplink carrierconfiguration, then the procedure proceeds to step 945. The multipleserving cells can be configured with uplink carriers according to theinformation of the RRC Control message including MAC-MainConfig or hasbeen configured with uplink carriers already before receiving the RRCcontrol message.

If the procedure proceeds to step 940, this means that the UE hasreceived the command for use of normal PHR MAC CE although multiplecells are configured with uplink carriers. Accordingly, the UEdetermines occurrence of unexpected error and ignores the information tomaintain the normal PHR MAC CE formation at step 940. However, the UEprocesses other control information included in the RRC control messagenormally with the exception of the erroneous information.

In order to determine whether the PHR MAC CE format is changed, the UEdetermines whether the most lately received MAC-MainConfig includesextendedPHR at step 945 and, if so, the procedure proceeds to step 955and, otherwise, the procedure proceeds to step 950.

If the procedure proceeds to step 955, this means that the PHR MAC CEformat is changed from extended PHR MAC CE formation to normal PHR MACCE format. Accordingly, the UE triggers PHR with the normal PHR MAC CEformat when the uplink resource for new transmission is available. Ifthe simultaneous PUSCH and PUCCH transmission is configured, the UEselects and includes the type 1 PH in the PH field. Otherwise, if thesimultaneous PUSCH and PUCCH transmission is not configured, this meansthat type 2 PH is out of consideration and thus there is no need forselection. The UE calculates the type 1 PH for the primary serving celland includes the type 1 PH in the PH field of the normal PHR MAC CEformat. Finally, the UE transmits the PHR MAC CE to the eNB at step 960and terminates the procedure.

For reference, the type 1 PH is determined in consideration of the PUSCHtransmit power, and type 2 PH is determined in consideration of both thePUSCH and PUCCH transmission powers.

According to exemplary embodiments of the present invention, the P bitis the first bit of PH byte (e.g., a byte having PH field). An exemplaryembodiment of the present invention includes a method for setting thefirst bit according to the PHR MAC CE format which is currently used bythe UE. If the currently used PHR MAC CE format is the normal PHR MAC CEformat, the UE sets the first bit to 0 even though the condition forsetting the P bit to 1 is satisfied. This is because if the eNBreceiving the PHR in normal format is a legacy eNB, then it is expectedthat the first bit of the PH byte is set to 0 such that, if this bit isset to 1, then the eNB is likely to malfunction. Otherwise, if the PHRMAC CE format is the extended PHR MAC CE format, this means that the eNBis of interpreting the P bit correctly such that UE sets the P bitnormally.

FIG. 10 is a flowchart illustrating a Power Headroom Report (PHR) methodaccording to an exemplary embodiment of the present invention.

The UE is allocated uplink resource for new transmission at step 1005and determines whether PHR is triggered at step 1010. For example, theUE operation at step 1010 is identical with the operation at step 820 ofFIG. 8.

If it is determined that no PHR is triggered at step 1010, then the UEwaits for allocation of uplink resource for new transmission whileperforming normal operation. If PHR is triggered at step 1010, then theprocedure proceeds to step 1015. At step 1015, the UE determines whetherpower backoff due to power management as allowed by P-MPR is applied forcalculating PH or P_(CMAX,c). In more detail, the UE determines whetherthe maximum transmit power is influenced by the P-MPR for powermanagement. For example, the UE determines whether the P_(CMAX,c) ischanged to a different value by the P-MPR for power management. If it isdetermined that the power backoff due to power management as allowed byP-MPR is not applied for calculating PH or P_(CMAX,c), then theprocedure proceeds to step 1025. Otherwise, the procedure proceeds tostep 1020.

At step 1020, the UE determines whether the current PHR MAC CE format isthe extended PHR MAC CE format. In other words, the UE determineswhether the most lately received MAC-MainConfig includes extendedPHRand, if so, the procedure proceeds to step 1030 and, otherwise, step1025. At step 1030, the UE set the first bit of the PH byte to 1 (i.e.sets the P bit to 1) and transmits the PHR MAC CE. At step 1025, the UEsets the first bit of the PH byte to 0 (i.e., sets the P bit to 0) andtransmits the PHR MAC CE.

FIG. 11 is a block diagram illustrating a configuration of an UserEquipment (UE) according to an exemplary embodiment of the presentinvention.

Referring to FIG. 11, the UE according to exemplary embodiments of thepresent invention includes a transceiver 1105, a controller 1110, amultiplexer/demultiplexer 1120, a control message processor 1135, andhigher layer processors 1125 and 1130.

The transceiver 1105 receives data and control signal on the downlinkchannel, and transmits data and control signal on the uplink channel ina serving cell. If multiple serving cells are configured, thetransceiver 1105 transmits and receives data and control signals in themultiple serving cells.

The multiplexer/demultiplexer 1102 multiplexes the data generated by thehigher layer processors 1125 and the control message processor 1135, anddemultiplexes the data received by the transceiver and delivers thedemultiplexed data to the higher layer processor 1125 and 1130 and/orthe control message processor 1135.

The control message processor 1135 processes the control messagereceived from the eNB and takes an appropriate action. That is, thecontrol message processor 1135 is responsible for configuring PHRfunction by referencing the control information such as MAC-MainConfigincluded in the RRC control message.

Each of the higher layer processors 1125 and 1130 is configured perservice and processes the data generated in association with the userservice such as File Transfer Protocol (FTP) and Voice over InternetProtocol (VoIP) to the multiplexer/demultiplexer 1120 or processes thedata from the multiplexer/demultiplexer 1120 to the higher layer serviceapplication.

The controller 1110 checks the scheduling command (e.g. uplink grants)received through the transceiver 1105, and controls the transceiver 1105and multiplexer/demultiplexer 1120 to perform uplink transmission withappropriate transmission resource at appropriate timing. The controller1110 calculates uplink transmit power per cell, determines whether totrigger PHR, and set P bit.

Although the description is directed to the case where the controller1110, the multiplexer/demultiplexer 1120, the control message processor1135, and higher layer processors 1125 and 1130 are implemented asseparate function blocks responsible for different functions forconvenience of technical explanation, the UE is not limited to thisconfiguration. For example, the functions of themultiplexer/demultiplexer 1120, the control message processor 1135, andthe higher layer processors 1125 and 1130 can be performed by thecontroller 1110.

As described above, the Power Headroom Report method and apparatus ofthe exemplary embodiments of the present invention is advantageous toreport the UE's Power Headroom per cell efficiently in the systemoperating in Carrier Aggregation mode.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method by a terminal in a mobile communicationsystem, the method comprising: determining whether power backoff isapplied due to power management if a power headroom report (PHR) istriggered; identifying whether an extended PHR is configured; generatingan extended power headroom (PH) medium access control (MAC) controlelement (CE) if the extended PHR is configured; and transmitting theextended PH MAC CE to a base station, wherein a first bit of an octetcontaining PH field in the extended PH MAC CE is set based on thedetermination.
 2. The method of claim 1, further comprising: generatinga PH MAC CE if the extended PHR is not configured; transmitting the PHMAC CE to the base station, wherein a first bit of the PH MAC CE is setto
 0. 3. The method of claim 1, wherein the first bit of the octetcontaining PH field in the extended PH MAC CE is set to 1, if the powerbackoff is applied due to the power management.
 4. A method by a basestation in a mobile communication system, the method comprising:transmitting configuration information to a terminal; and receiving anextended power headroom (PH) medium access control (MAC) control element(CE) from the terminal, if the configuration information configures anextended PHR, wherein a first bit of an octet containing PH field in theextended PH MAC CE is set based on a determination that whether powerbackoff is applied due to power management by the terminal.
 5. Themethod of claim 4, further comprising: receiving a PH MAC CE from theterminal, if the configuration information does not configure anextended PHR, wherein a first bit of the PH MAC CE is set to
 0. 6. Themethod of claim 4, wherein the first bit of the octet containing PHfield in the extended PH MAC CE is set to 1, if the power backoff isapplied due to the power management.
 7. A terminal in a mobilecommunication system, the terminal comprising: a transceiver configuredto transmit and receive a signal; and a controller configured: todetermine whether power backoff is applied due to power management if apower headroom report (PHR) is triggered, to identify whether anextended PHR is configured, generating an extended power headroom (PH)medium access control (MAC) control element (CE) if the extended PHR isconfigured, and to transmit the extended PH MAC CE to a base station,wherein a first bit of an octet containing PH field in the extended PHMAC CE is set based on the determination.
 8. The terminal of claim 7,wherein the controller is further configured: to generate a PH MAC CE ifthe extended PHR is not configured, and to transmit the PH MAC CE to thebase station, wherein a first bit of the PH MAC CE is set to
 0. 9. Theterminal of claim 7, wherein the first bit of the octet containing PHfield in the extended PH MAC CE is set to 1, if the power backoff isapplied due to the power management.
 10. A base station in a mobilecommunication system, the base station comprising: a transceiverconfigured to transmit and receive a signal; and a controllerconfigured: to transmit configuration information to a terminal, and toreceive an extended power headroom (PH) medium access control (MAC)control element (CE) from the terminal, if the configuration informationconfigures an extended PHR, wherein a first bit of an octet containingPH field in the extended PH MAC CE is set based on a determination thatwhether power backoff is applied due to the power management by theterminal.
 11. The base station of claim 10, wherein the controller isfurther configured to receive a PH MAC CE from the terminal, if theconfiguration information does not configure an extended PHR, andwherein a first bit of the PH MAC CE is set to
 0. 12. The base stationof claim 10, wherein the first bit of the octet containing PH field inthe extended PH MAC CE is set to 1, if the power backoff is applied dueto the power management.